[flang] Add semantics test for EVENT WAIT statement

[ngeorge1098]

Add non-standard-conforming statement for errmsg specifier.
Remove redundant non-standard-conforming statement for
event-variable. Change language of comments to properly
reflect the language of the standards.

[ktras]

LGTM

flang/test/Semantics/event02.f90

+! RUN: %python %S/test_errors.py %s %flang_fc1
+! This test checks for semantic errors in event wait statements based on the
+! statement specification in section 11.6.8 of the Fortran 2018 standard.
+
+program test_event_wait
+  use iso_fortran_env, only : event_type
+  implicit none
+
+  ! event_type variables must be coarrays
+  type(event_type) non_coarray
+
+  type(event_type) concert[*], occurrences(2)[*]
+  integer threshold, indexed(1), non_event[*], sync_status, co_indexed_integer[*], superfluous_stat, non_scalar(1)
+  character(len=128) error_message, non_scalar_char(1), co_indexed_character[*], superfluous_errmsg
+  logical invalid_type
+
+  !_______________________ standard-conforming statement ___________________________
+
+  event wait(concert)
+  event wait(occurrences(1))
+  event wait(concert, until_count=threshold)
+  event wait(concert, until_count=indexed(1))
+  event wait(concert, until_count=co_indexed_integer[1])
+  event wait(concert,                        stat=sync_status)
+  event wait(concert, until_count=threshold, stat=sync_status)
+  event wait(concert,                                          errmsg=error_message)
+  event wait(concert, until_count=threshold,                   errmsg=error_message)
+  event wait(concert,                        stat=sync_status, errmsg=error_message)
+  event wait(concert, until_count=threshold, stat=sync_status, errmsg=error_message)
+
+  !____________________ non-standard-conforming statement __________________________
+
+  !_________________________ invalid event-variable ________________________________
+
+  ! event-variable must be event_type
+  event wait(non_event)
+
+  ! event-variable must be a coarray
+  event wait(non_coarray)
+
+  ! event-variable must not be coindexed
+  event wait(concert[1])
+
+  ! event-variable must not be coindexed
+  event wait(occurrences(1)[1])
+
+  ! event-variable must be a scalar variable
+  event wait(occurrences)
+
+  ! event-variable has an unknown expression
+  !ERROR: expected ')'
+  event wait(event=concert)
+
+  !_____________ invalid event-wait-spec-lists: invalid until-spec _________________
+
+  ! Invalid until-spec keyword
+  !ERROR: expected ')'
+  event wait(concert, until_amount=threshold)
+
+  ! Until-spec must be an integer scalar
+  event wait(concert, until_count=invalid_type)
+
+  ! Until-spec must be an integer scalar
+  event wait(concert, until_count=non_scalar)
+
+  ! Invalid until-spec: missing until-spec variable
+  !ERROR: expected ')'
+  event wait(concert, until_count)
+
+  ! Invalid until-spec: missing 'until_count='
+  !ERROR: expected ')'
+  event wait(concert, threshold)
+
+  !_________________ invalid sync-stat-lists: invalid stat= ________________________
+
+  ! Invalid stat-variable keyword
+  !ERROR: expected ')'
+  event wait(concert, status=sync_status)
+
+  ! Stat-variable must be an integer scalar
+  event wait(concert, stat=invalid_type)
+
+  ! Stat-variable must be an integer scalar
+  event wait(concert, stat=non_scalar)
+
+  ! Invalid sync-stat-list: missing stat-variable
+  !ERROR: expected ')'
+  event wait(concert, stat)
+
+  ! Invalid sync-stat-list: missing 'stat='
+  !ERROR: expected ')'
+  event wait(concert, sync_status)
+
+  !________________ invalid sync-stat-lists: invalid errmsg= _______________________
+
+  ! Invalid errmsg-variable keyword
+  !ERROR: expected ')'
+  event wait(concert, errormsg=error_message)
+
+  ! Errmsg-variable must be a character scalar
+  event wait(concert, errmsg=invalid_type)
+
+  ! Errmsg-variable must be a character scalar
+  event wait(concert, errmsg=non_scalar_char)
+
+  ! Invalid sync-stat-list: missing 'errmsg='
+  !ERROR: expected ')'
+  event wait(concert, error_message)
+
+  ! Invalid sync-stat-list: missing errmsg-variable
+  !ERROR: expected ')'
+  event wait(concert, errmsg)
+
+  !______________ invalid event-variable: redundant event-variable _________________
+
+  !ERROR: expected ')'
+  event wait(concert, occurrences(1))
+
+  !ERROR: expected ')'
+  event wait(concert, occurrences(1), stat=sync_status, errmsg=error_message)
+
+  !______ invalid event-wait-spec-lists: redundant event-wait-spec-list ____________
+
+  ! No specifier shall appear more than once in a given event-wait-spec-list
+  event wait(concert, until_count=threshold, until_count=indexed(1))
+
+  ! No specifier shall appear more than once in a given event-wait-spec-list
+  event wait(concert, stat=sync_status, stat=superfluous_stat)
+
+  ! No specifier shall appear more than once in a given event-wait-spec-list
+  event wait(concert, errmsg=error_message, errmsg=superfluous_errmsg)
+
+  !_____________ invalid sync-stat-lists: coindexed stat-variable __________________
+
+  ! Check constraint C1173 from the Fortran 2018 standard
+  event wait(concert, stat=co_indexed_integer[1])
+
+  ! Check constraint C1173 from the Fortran 2018 standard
+  event wait(concert, errmsg=co_indexed_character[1])
+
+end program test_event_wait